1. Field of the Invention
The present invention relates to a two-rear-wheel electric vehicle configured to lean its vehicle body when turning.
2. Description of the Related Art
Examples of a conventional two-rear-wheel electric vehicle include a two-rear-wheel electric vehicle disclosed in Japanese Patent Application Laid-Open No. 5-213253.
In the two-rear-wheel electric vehicle disclosed in Japanese Patent Application Laid-Open No. 5-213253, a pair of right and left electric power units are located below a central portion of a vehicle body frame. The right and left electric power units are configured to drive the respective rear wheels. Each of the electric power units includes a drive motor, a primary speed reduction mechanism that reduces the speed of a rotational drive force supplied from the drive motor, a power transmission mechanism that transmits the rotational drive force whose speed has been reduced to the rear wheel side, and a secondary speed reduction mechanism that reduces the speed of the rotational drive force transmitted from the power transmission mechanism. Each of the electric power units constitutes a swing arm. The secondary speed reduction mechanism transmits the rotational drive force to the rear wheel that is supported on a rear end portion of the corresponding electric power unit. The electric vehicle also includes a pair of right and left shock absorber units each located between an upper rear portion of the vehicle body frame and the rear end portion of the corresponding electric power unit.
The two-rear-wheel electric vehicle disclosed in Japanese Patent Application Laid-Open No. 5-213253 also includes a frame holder assembly that is fixed by a lower central portion and the upper rear portion of the vehicle body frame. A battery is located in the frame holder assembly.
Such a two-rear-wheel electric vehicle is able to stand on its own because a pair of right and left rear wheels are provided. Therefore, a driving operation is relatively easy when the vehicle is running at a low speed. Additionally, the two-rear-wheel electric vehicle can be caused to run by less power than a four-wheel vehicle can, and has a more excellent loading capacity than a two-wheel vehicle does. Thus, the two-rear-wheel electric vehicle achieves stable running under a state where a large amount of baggage is loaded thereon. The two-rear-wheel electric vehicle includes a battery serving as a power source. Since a possible travel distance obtained per charging is limited by the capacity of the battery, the two-rear-wheel electric vehicle is better suited for a short-distance travel than a long-distance travel.
Moreover, the two-rear-wheel electric vehicle disclosed in Japanese Patent Application Laid-Open No. 5-213253, which is not able to lean its vehicle body when turning, needs to maintain the attitude of the vehicle body against a centrifugal force while the vehicle is running on a curve.
In this respect, a two-rear-wheel electric vehicle configured to lean its vehicle body when turning is allowed to turn with the vehicle body leaning to the inner side of a curve. This provides a high stability while the vehicle is running on a curve, and does not require high driving skill.
In view of the above, a two-rear-wheel electric vehicle configured to lean its vehicle body when turning is a vehicle suitable for, for example, purposes of short-distance delivery services or purposes (such as shopping) intimately involved in daily lives of females and the elderly.
In consideration of use for the purposes of short-distance delivery services or purposes intimately involved in daily lives of females and the elderly, a high degree of convenience is demanded of the two-rear-wheel electric vehicle configured to lean its vehicle body when turning. To be specific, the convenience includes requiring a reduced frequency of charging, having a low weight to provide easy handling, and the like.
As for the frequency of charging, in general, a vehicle including an engine does not require much time for refueling with gasoline, but an electric vehicle requires relatively much time for charging a battery. For example, in a case where a user, when carrying out a delivery service, notices that a remaining battery charge of the electric vehicle is low but there is no time for charging, the delivery service may be disabled. In a case where a user, when going out for an urgent matter, notices that a remaining battery charge of the electric vehicle is low but there is no time for charging, the user has to abandon going out with the electric vehicle. Similarly, the electric vehicle may force the user to refrain from the use thereof when the remaining battery charge is low. Thus, a reduced frequency of charging is preferable in the two-rear-wheel electric vehicle configured to lean its vehicle body when turning. In other words, a large battery capacity is preferred, and less power consumption is preferred.
Here, the two-rear-wheel electric vehicle includes two rear wheels, and therefore the weight of the vehicle body is in general larger than that of a two-wheel vehicle. An increase in the weight of the vehicle body leads to an increase in power consumption. In order to reduce the frequency of charging, the battery capacity needs to be increased. In the two-rear-wheel electric vehicle according to Japanese Patent Application Laid-Open No. 5-213253 as well, in order to increase the battery capacity, a wide space is necessary for installation of the battery.
However, using a large-size battery for the increase in the battery capacity causes not only an increase in the weight of the battery but also the need to increase the weight of the vehicle body frame because the rigidity of the vehicle body frame must be ensured, which results in a further increase in the weight of the vehicle body. A vicious cycle follows in this manner. Additionally, an increase in the weight of the vehicle body makes the handling of the vehicle body difficult, which deteriorates the convenience. Therefore, how to achieve a weight reduction of the vehicle body while ensuring a large battery capacity is a problem.